NCBI Summary:
The mitochondrial oxidation of long-chain fatty acids is initiated by the sequential action of carnitine palmitoyltransferase I (which is located in the outer membrane and is detergent-labile) and carnitine palmitoyltransferase II (which is located in the inner membrane and is detergent-stable), together with a carnitine-acylcarnitine translocase. CPT I is the key enzyme in the carnitine-dependent transport across the mitochondrial inner membrane and its deficiency results in a decreased rate of fatty acid beta-oxidation.

General function

Metabolism

Comment

Cellular localization

Mitochondrial

Comment

Ovarian function

Oocyte maturation

Comment

Changes in gene expression involved in energy utilization during chicken follicle development Seol HS, et al .
Ovarian follicle development in egg-laying species is characterized by rapid growth in 7 days prior to ovulation when DNA and protein synthesis is markedly increased in the granulosa and theca cells. However, energy and substrate sources to facilitate the extensive DNA and protein synthesis necessary for folliculogenesis have not been identified in avian species. The current study was undertaken to investigate the expression profiles of regulatory genes involved in glucose transport, glycolysis and fatty acid oxidation in the follicle membranes from the small white follicle (SWF) to follicle 1 (F1) stages of follicle development. In our analysis of glucose transporter (GLUT) isoform expression, the level of GLUT1 mRNA increased with follicle development while GLUT2, GLUT3 and GLUT8 mRNA levels were unaffected by follicle development. In contrast, the expression patterns of proteins involved in metabolism down-stream of glucose transport, including hexokinase (HK), pyruvate dehydrogenase E1alpha (PDH E1alpha) and citrate synthase (CS), did not vary with the developmental stage of the follicle, even during rapid follicle growth. Expression of genes related to beta-oxidation of fatty acids (carnitine palmityl CoA transferase I and II, l-3-hydroxyacyl CoA dehydrogenase and long-chain acyl-CoA dehydrogenase), for which expression in the ovarian follicles of mammalian species has not previously been studied, was not changed consistently with the follicle development. These results suggest that both glucose and fatty acids might work as energy sources to ensure rapid follicle development in the chicken ovary, even though glycolysis and beta-oxidation are not modulated by follicle development.

Expression regulated by

Comment

Ovarian localization

Cumulus

Comment

Fatty acid synthesis and oxidation in cumulus cells support oocyte maturation in bovine. Sanchez-Lazo L 2014 et al.
Oocyte meiotic maturation requires energy from various substrates including glucose, amino acids and lipids. Mitochondrial fatty acid (FA) beta-oxidation (FAO) in the oocyte is required for meiotic maturation, which is accompanied by differential expression of numerous genes involved in FA metabolism in surrounding cumulus cells (CC) in vivo. The objective was to elucidate components involved in FA metabolism in CC during oocyte maturation. Twenty-seven genes related to lipogenesis, lipolysis, FA transport and FAO were chosen from comparative transcriptome analysis of bovine CC before and after maturation in vivo. Using real time PCR, 22 were significantly up-regulated at different times of in vitro maturation (IVM) in relation to oocyte meiosis progression from germinal vesicle (GV) breakdown to metaphase-II. Proteins FA synthase, acetyl-Co-A carboxylase, carnitine palmitoyltransferase CPT1, perilipin 2 and FA binding protein FABP3 were detected by western blot and immunolocalized to CC and oocyte cytoplasm, with FABP3 concentrated around oocyte chromatin. By mass spectrometry, CC lipid profiling was shown to be different before and after IVM. FAO inhibitors etomoxir and mildronate dose-dependently decreased oocyte maturation rate in vitro. In terms of viability, cumulus enclosed oocytes were more sensitive to etomoxir than denuded oocytes. In CC, etomoxir (150 M) led to down-regulation of lipogenesis genes and up-regulated lipolysis and FAO genes. Moreover, the number of lipid droplets decreased whereas several lipid species were more abundant compared to non-treated CC after IVM. In conclusion, FA metabolism in CC is important to maintain metabolic homeostasis and may influence meiosis progression and survival of enclosed oocytes.
/////////////////////////
Fatty acid oxidation and meiotic resumption in mouse oocytes. Downs SM et al. We have examined the potential role of fatty acid oxidation (FAO) in AMP-activated protein kinase (AMPK)-induced meiotic maturation. Etomoxir and malonyl CoA, two inhibitors of carnitine palmitoyl transferase-1 (CPT1), and thus FAO, blocked meiotic induction in dbcAMP-arrested cumulus cell-enclosed oocytes (CEO) and denuded oocytes (DO) by the AMPK activator, AICAR. C75, an activator of CPT1 and FAO, stimulated meiotic resumption in CEO and DO. This effect was insensitive to the AMPK inhibitor, compound C, indicating an action downstream of AMPK. Palmitic acid or carnitine also promoted meiotic resumption in DO in the presence of AICAR. Since C75 also suppresses the activity of fatty acid synthase (FAS), we tested another FAS inhibitor, cerulenin. Cerulenin stimulated maturation in arrested oocytes, but to a lesser extent, exhibited significantly slower kinetics and was effective in CEO but not DO. Moreover, etomoxir completely blocked C75-induced maturation but was ineffective in cerulenin-treated oocytes, suggesting that the meiosis-inducing action of C75 is through activation of FAO within the oocyte, while that of cerulenin is independent of FAO and acts within the cumulus cells. Finally, we determined that long chain, but not short chain, fatty acyl carnitine derivatives were stimulatory to oocyte maturation. Palmitoyl carnitine stimulated maturation in both CEO and DO, with rapid kinetics in DO; this effect was blocked by mercaptoacetate, a downstream inhibitor of FAO. These results indicate that activation of AMPK stimulates meiotic resumption in mouse oocytes by eliminating a block to FAO. Mol. Reprod. Dev. 2009. (c) 2009 Wiley-Liss, Inc.